1. Field of the Invention
The present invention relates to a cooling apparatus for cooling an electronic component including a CPU or MPU.
2. Description of the Related Art
CPUs (central processing units) or MPUs (micro processing Units) are key parts of computers for processing data to obtain results and outputting the results. The CPUs or MPUs are installed in high performance electronic devices. In recent years, clock frequency of CPUs or MPUs has been rapidly increased. This results in a continuous increase in heat generation thereof and therefore increases the temperature of the CPUs or MPUs. The temperature increase in CPUs or MPUs, however, may cause malfunction of the CPUs or MPUs. In order to prevent malfunction, it is crucial to cool the CPUs or MPUs. For this reason, an electronic component which generates heat, e.g., a CPU or an MPU, is used together with a cooling device for cooling it, when being arranged in a high performance electronic device.
A heat sink fan including a heat sink and a cooling fan mounted thereon is a typical cooling device used for the high performance electronic device. The heat sink is typically made of metal and has a plurality of heat-dissipating fins for increasing a total surface area of the heat sink. The cooling fan mounted on the heat sink supplies the heat sink with air. The heat sink fan is arranged in the high performance electronic device such that the heat sink is in contact with the heat generating component and the heat sink is forcibly cooled by the air from the cooling fan.
In recent years, operation speed of CPUs or MPUs has been increasing. Due to this, it is necessary to improve cooling efficiency of the heat sink fans used together with the CPUs or MPUs, and therefore improve heat transfer efficiency from the CPUs or MPUs to the heat sinks.
As stated above, the cooling efficiency of the heat sink is increased as the surface area thereof is increased. Therefore, the surface area of the entire heat sink has to be increased to improve the cooling efficiency of the heat sink. To increase the surface area of the heat sink, it may be one solution to form the heat-dissipating fins extremely small in circumferential thickness, arrange as many heat-dissipating fins as possible, and form each heat-dissipating fin so as to extend radially outward from a base portion of the heat sink. The thinned fins, however, deteriorate the heat sink in strength, and therefore, there exists a lower limitation in the thickness. Further, the configuration, where many heat-dissipating fins are arranged and each and every one of the heat-dissipating fins extends radially outward from the base portion, narrows each space between adjacent ones of the heat-dissipating fins because the adjacent ones come close. As a result, air blown to the heat sink is prevented from smoothly passing through the spaces between the adjacent heat-dissipating fins. Thus, simply increasing the surface area of the heat sink does not necessarily improve the cooling efficiency.
In a general configuration, the cooling fan is mounted on the heat sink, the cooling fan operates to send air to the heat sink, and thereby, heat transferred to the heat sink is dissipated. An improvement in the cooling efficiency of the heat sink can lower a rotational speed of the cooling fan mounted on the heat sink, and thereby, reduce a noise. In recent years, electronic devices having a CPU or MPU installed therein have become mainly used in quiet spaces, such as private homes and office rooms, and therefore, are required to be quieter. Thus, a heat sink higher in cooling characteristics and lower in noise is required.